docs: copy in waitForElement docs (testing-library#73)

* Copy in waitForElement docs * Link out to source * Add waitForElement examples

Author: alexkrolick

README.md

@@ -86,6 +86,7 @@ facilitate testing implementation details). Read more about this in
  * [`cleanup`](#cleanup)
  * [`Simulate`](#simulate)
  * [`wait`](#wait)
+ * [`waitForElement`](#waitforelement)
  * [`fireEvent(node: HTMLElement, event: Event)`](#fireeventnode-htmlelement-event-event)
 * [`TextMatch`](#textmatch)
 * [`query` APIs](#query-apis)
@@ -373,6 +374,39 @@ The default `interval` is `50ms`. However it will run your callback immediately
 on the next tick of the event loop (in a `setTimeout`) before starting the
 intervals.
 
+### `waitForElement`
+
+See [dom-testing-library#waitForElement](https://github.com/kentcdodds/dom-testing-library#waitforelement)
+
+```js
+await waitForElement(() => getByText('Search'))
+```
+
+<details>
+ <summary>
+ Example
+ </summary>
+
+```diff
+test('should submit form when valid', async () => {
+ const mockSubmit = jest.fn()
+ const {
+ container,
+ getByLabelText,
+ getByText
+ } = render(<Form onSubmit={mockSubmit} />)
+ const nameInput = getByLabelText('Name')
+ nameInput.value = 'Chewbacca'
+ Simulate.change(nameInput)
++ // wait for button to appear and click it
++ const submitButton = await waitForElement(() => getByText('Search'))
++ Simulate.click(submitButton)
++ expect(mockSubmit).toBeCalled()
+})
+```
+
+</details>
+
 ### `fireEvent(node: HTMLElement, event: Event)`
 
 Fire DOM events.